"We're in the pre-negotiation phase of what will be a very complex and very tough two year negotiation," the senior Conservative said.

"The numbers that have been bandied around in the press – €50bn, €60bn, €100bn – we don't recognise.

"What we have said throughout is that we will meet our international negotiations and we will go into the negotiations in the best interest of both us and the European Union."

The event came just an hour before the EU's chief Brexit negotiator, Michel Barnier, addressed reporters in Brussels. Barnier ruled out a "punishment" for the UK. "There's no Brexit bill. The financial settlement is only about settling the accounts," he added.

But the French politician later warned of "explosive" consequences if the UK failed to meet its liabilities as it split from the EU.

"The EU 27 is on track to make sure that UK's withdrawal happens in an orderly fashion. The UK's decision to leave the EU has now caused 10 months of uncertainty. We need to remove that uncertainty. It's high time to start negotiating...the clock is ticking," Barnier said.

The developments follow leaks of a Downing Street summit between May, David and EU Commission President Jean Claude Juncker.

Juncker reportedly told German Chancellor Angela Merkel was "living on another planet" over Brexit, whilst May has vowed to be a "bloody difficult woman" during the two-year-talks.

"We don't comment on private meetings, we never have and we never will," Davis told reporters. "What I will say to you is that the morning after [the meeting] both Downing Street and the European Commission said they were constructive talks."